<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <button>按钮5</button>
    <script>
        //1.获取所有按钮元素
        var btns = document.getElementsByTagName('button');
        //btns得到的是伪数组  里面的每一个元素 btns[i]
        for(var i = 0; i < btns.length; i++){
            btns[i].onclick = function(){
                //(1)先把所有的背景颜色去掉
                for(var i = 0; i < btns.length; i++){
                    btns[i].style.backgroundColor = '';
                }
                //(2)然后让当前元素背景颜色为pink
                this.style.backgroundColor = 'pink';
            }
        }
    </script>
</body>
</html>